1. Field of the Invention
The invention relates to a circuit configuration and, in particular, to a switch mode power supply or the like.
Transformer devices that interact with specific semiconductor components are used in many circuit configurations. In such a case, the transformer devices have at least one input electrode and one output electrode. The semiconductor components themselves have at least one first connecting region and one second connecting region. Certain circuit configurations provide for a semiconductor component to be electrically connected by at least one of the connecting regions to the input electrode and/or to the output electrode of the transformer device, to be precise without the interposition of any further components.
Such conventional circuit configurations have the problem that prior art transformer devices are based on the principle of electromagnetic energy conversion. In such a case, an input voltage signal, which is applied to the input electrode, is first of all converted to a magnetic field through a corresponding current flow. This takes place, for example, by current flowing in a primary coil of the transformer device. The magnetic field that is produced in the primary coil is then transmitted to a secondary region having a secondary coil through a magnetic coupling—for example, through a ferrite core or the like, in which secondary coil the magnetic induction in the primary coil induces an electrical voltage, which can then be tapped off at the output electrode. A corresponding transformation ratio is defined between the input voltage and the output voltage by the choice of the coil parameters, in particular, by the choice of the numbers of turns.
One problem in such a case is that the increase in voltage, that is to say, the transformer effect, is produced through the magnetic field transmission. The configuration of every circuit configuration, that is to say, in particular, as a result of the contact-making lines and board substrates, results in parasitic inductances or stray inductances. Any changes in the magnetic field, in particular, in the magnetic field in the region of the transformer device, automatically leads to induction voltages resulting from the stray inductances. Even in the case of rapid switching processes and, in particular, in the immediate vicinity, that is to say, even in the case of the semiconductor components that are connected directly to the transformer device, the induction voltages and the electric currents that are forced to flow as a result thereof assume a considerable magnitude such that the circuit regions in which these induction currents or induction voltages occur and, in particular, the corresponding semiconductor components, may subsequently have their characteristics changed or even damaged. Furthermore, the stray inductances have a disadvantageous effect on radio suppression.
Previous efforts to ameliorate the hazards resulting from induced voltages or currents have been directed at keeping the parasitic inductances or stray inductances as low as possible, especially in the region of those semiconductor components that make direct contact with the transformer device. On the other hand, certain protection circuits have been integrated in the circuit configurations, for example, in the form of so-called snubbers, but these increase the circuitry complexity and the area required for the circuit configuration.
2. Summary of the Invention
It is accordingly an object of the invention to provide a circuit configuration and, in particular, a switch-mode power supply, that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that allow operation of semiconductor components, which are connected to a transformer device, in a particularly protected manner.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a circuit configuration, including an electromechanical conversion transformer having at least one input electrode and at least one output electrode, at least one semiconductor component having at least one first connecting region and at least one second connecting region, and the semiconductor component directly mechanically and electrically connected by at least one of the first connecting region and second connecting region to at least one of the input electrode and the output electrode.
In accordance with another feature of the invention, the semiconductor component has at least one connecting region and the transformer has at least one connecting region substantially mechanically identical to the connecting region of the semiconductor component.
The circuit configuration according to the invention and, in particular, the switch-mode power supply according to the invention are characterized in that the transformer device is in the form of an electromechanical conversion device.
One basic idea of the present invention is, thus, to reduce or to avoid the influence of any stray inductances or parasitic inductances that may be present by dispensing with the activity of the transformer device to transmit a magnetic field. The lack of such a transmitting magnetic field also means that the parasitic inductances or stray inductances are not critical because induced voltages or currents also may largely disappear when there are no alternating magnetic fields. The fundamental principle in this case is that electromechanical coupling in the transformer device produces the conversion effect.
In such a case, in accordance with a further feature of the invention, it is particularly advantageous for the transformer device to be in the form of a piezo-transformer or the like. Such a piezo-transformer makes use of the so-called piezoelectric effect in a corresponding material. The input voltage is supplied through the input electrode to the material that is provided for the electromechanical conversion. The electric field that is formed in the material that is provided for the electromechanical conversion changes the geometric structure of this material in accordance with the piezoelectric effect. This geometric change may be detectable externally as a mechanical or micromechanical movement. On the other hand, in accordance with the piezoelectric effect, any mechanical movement of the material that is provided for the electromechanical conversion results in a corresponding change in the electrical field strength distribution. Consequently, a correspondingly transformed output voltage can be tapped off at an output electrode at some other point on the material that is provided for the conversion process. If the input electrode and the output electrode are disposed at different positions on the material that is provided for the conversion process, then the input voltage and the output voltage arc normally also different to one another.
In addition to avoiding or reducing the risk caused by induction voltages that are transmitted through the parasitic inductances, the use of an electromechanical conversion device also results in the advantage that the components of the circuit configuration and, in particular, the semiconductor components that are provided and are intended to make direct contact with the transformer device can be fitted physically more closely to the transformer device because the respective transformer device now no longer produces any stray magnetic fields.
Thus, In accordance with an added feature of the invention, it is possible to produce, in particular, the switch-mode power supply with a more compact construction. It is particularly advantageous for the semiconductor component to be formed in each case with at least one connecting region that is connected substantially directly mechanically and/or electrically to the input electrode and/or to the output electrode. This means that the first and/or second connecting region of each semiconductor component can be fitted directly to the input electrode or to the output electrode, without the interposition of a line device.
In accordance with an additional feature of the invention, the substantially direct mechanical and/or electrical connection is advantageously respectively formed by a solder region, an adhesive region, and/or the like.
In accordance with yet another feature of the invention, the configuration and the structure of the substantially direct mechanical and/or electrical connection between the input electrode/output electrode of the transformer device and the respective connecting region of the semiconductor component are particularly simple if the input electrode, the output electrode, the first connecting region, and/or the second connecting region are each substantially flat and/or planar, and/or have/has a respective flat and/or planar element for making contact.
In accordance with yet a further feature of the invention, materials such as silver, copper, compounds of silver and copper and/or similar materials and/or materials that contain silver, copper, compounds of silver and copper and/or the like are preferred to form the input electrode, the output electrode, the first connecting region, and/or the second connecting region.
In accordance with yet an added feature of the invention, a piezoelectric ceramic or the like is preferably used as the material for the electromechanical conversion.
In accordance with yet an additional feature of the invention, to carry out the transformation process, the invention provides that the transformer device and, in particular, the material for the electromechanical conversion thereof have a longitudinal extent and at least a transverse extent that are matched to a desired or intended transformation ratio of the transformer device.
In accordance with again another feature of the invention, for variation of the desired transformation ratio, the transformer device and, in particular, the material for the electromechanical conversion by the transformer device are substantially in the form of a cuboid, a cylinder, and/or the like.
In accordance with again a further feature of the invention, the semiconductor component is in the form of a diode, a switching device, a transistor device, and/or the like. An appropriate number of semiconductor components of the type just mentioned may be provided, if necessary, also in mixed form.
In accordance with a concomitant feature of the invention, there is provided a cooling element is provided on the input electrode and/or on the output electrode of the transformer device together with a respective connecting region of the semiconductor component, in particular, for cooling of the semiconductor component and/or of the transformer device.
Those aspects of the present invention that have been described above, as well as further aspects of the present invention, will be explained in more detail in the following description.
Magnetic components, such as transformers and inductors, are important components of pulsed switch-mode power supplies. Semiconductor components that are connected to magnetic components such as these, for example, switches or diodes or the like, should be positioned or provided in the immediate vicinity of these magnetic components to keep the unavoidable parasitic inductances as low as possible. These parasitic inductances or stray inductances are produced, for example, by wires, PCB conductor tracks, or by transformer windings or the like. Parasitic inductances between the transformer or the transformer device and the power semiconductors can lead to overvoltages, which are dangerous to the semiconductor, in the sense of induction voltages, in which case the induction voltage UL resulting from the parasitic or stray inductance L is associated with the rate of change of the current dI/dt in accordance with:UL=−L dI/dt.Such overvoltage UL can lead to a permanent change, damage, or destruction of the semiconductor, particularly, if its breakdown voltage is exceeded.
Such a problem of overvoltages resulting from induction through parasitic or stray inductances is a major aspect of the present invention.
Another aspect that the present invention is intended to deal with is the system miniaturization of circuit configurations with a transformer device and semiconductor components coupled thereto.
Nowadays, magnetic elements such as transformers or the like and semiconductor components are provided as separate components. This results in a large amount of space being consumed in the circuit configurations, for example, on a board or the like. The proposed solution allows magnetic elements and the semiconductors that make contact with them to be combined as a compact component group. Specifically, compaction is accomplished by fitting the corresponding semiconductor components directly to the electrodes or the transformer devices, which are in the form of electromechanical conversion devices.
Conventional procedures for suppressing overvoltages require complex circuitry and prevent such a compact layout. By way of example, protection circuits are provided, for example, so-called snubbers. Such circuit complexity requires space in the region of the circuit configuration, which is contrary to the objective of system miniaturization.
Parasitic inductances can also be kept low by an optimized layout, although this results in certain circuitry restrictions.
With regard not only to the layout question but also to the provision of additional protection circuits, it must be remembered that these involve additional costs, firstly from the construction of these modified circuit configurations and secondly from the additional power losses that occur in the protection circuits.
In contrast, the modern further development of conventional transformers as piezo-transformers offers a suitable starting point to avoid the disadvantages of the prior art. This new type of transformer is not based on any form of electromagnetic energy conversion, but on electromechanical energy conversion. The electrical signal that is applied to an input electrode produces a mechanical oscillation in the material for the conversion process, for example, a piezoelectric ceramic, based on the time profile of the input voltage to the input electrode, which can be tapped off from the output electrode to an electrical signal converted back in the opposite sense.
The new physical form of piezo-transformers allows greater system integration and miniaturization of semiconductor and transformer. Semiconductors can be fitted directly on the input electrode or on the output electrode of the piezo-transformer, where they can be adhesively bonded on, or soldered on, for example. In such a case, the electrical connection between the semiconductor component and the electrode of the piezo-transformer can be produced over a large area, using the lower face of the semiconductor. When using flip chip semiconductors, contact can also be made with the second face of the semiconductor. Such a configuration eliminates or reduces the parasitic inductance of the supply line.
In addition, if the electrodes of the piezo-transformer are constructed to be sufficiently large, it is also possible to fit heat sinks to the electrodes or to the electrode of the piezo transformer. Such a configuration, thus immediately allows better cooling of the transformer and, in particular, of the semiconductor component that is provided thereon.
Overall, the procedure according to the invention has the following advantages:                elimination or reduction of parasitic inductances in the configuration of a transformer device and semiconductor component;        elimination of protection circuits such as snubbers or the like;        augmentation of the switching frequencies;        expansion of the level of integration for further system miniaturization; and        simplification of radio suppression.        
In principle, virtually any topologies of circuit configurations and, in particular, of switch-mode power supplies may be used. In particular, any variants of flyback converters, forward converters, half bridges (half bridge converters), full bridges (bridge converters), Cuk converters, and the like may be used.
One fundamental aspect of the present invention is that semiconductor components are disposed directly on a piezo-transformer by soldering or adhesive bonding.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a circuit configuration and, in particular, a switch-mode power supply, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.